The present invention relates to an ocular iontophoresis device for delivering medication (into the eye).
The principle of ocular iontophoresis is applying an electric field to an electrolytic substance containing at least one medication, in order to transport the medication(s) into the body or the organ to be treated, via the biological membranes of the eye.
Like the brain, the eye is protected from the central venous system by biological barriers (hemo-ocular, hemo-aqueous, hemo-retinal) making it very difficult to administer medication at sufficient concentration, specifically to the posterior segment of the eye, in particular to the retina.
The systemic path (oral or intravenous) can thus administer only a very small fraction (a few %) of the initial quantity into the internal tissue of the eyes, and thus rapidly becomes insufficient.
That is why techniques of locally administering medication to the eye have been and are being developed, including the following:                direct injections around the eye (peribulbar, retrobulbar) or into the eye (intraocular), which remain very traumatic. Furthermore, the drug is always diluted rapidly, disappearing from the vitreous humor in a few days, or being rejected systemically. This mode of administration also presents risks of infection, of bleeding, of cataracts, and of detaching the retina. Finally, disorders such as glaucoma cannot be treated in this way because of the increase in intraocular pressure.        topical applications of drops, which do not treat the posterior segment since penetration is very limited (typically less than 5%) and which do not enable therapeutic concentrations to be reached beyond the anterior segment. In addition, tears wash the drug away quickly, ocular fluids opposing penetration and the diffusion path is then quite long. Applications need to be repeated frequently.        photodynamic therapy consists in injecting medication systemically and in activating it locally by using a laser at a certain wavelength, taking advantage of the transparency of the cornea. However drawbacks remain: the patient must remain in the dark, the medication must be modified by adding a photosensitive agent which prevents it from acting prior to being activated, and the doctor must possess equipment that is relatively expensive.        inserts in the form of reservoirs of medication placed on the surface of the eye (in non-invasive manner), such as lenses or preferably in the conjunctival sac, and serving to deliver medication in continuous or programmed manner. Numerous systems have been developed, either in the form of a lens or a ring, or in the form of a small lenticular or tubular reservoir placed in the conjunctival sac. The main drawbacks of these systems are firstly limited passage to the posterior segment which limits their use to pathologies of the anterior segment (inflammation, conjunctivitis), and secondly the risk of the insert being expelled.        intraocular implants for programmed release of medication are put into place surgically in the vitreous humor like Vitrarest® from Baush & Lomb, possibly fixed to the sclera like the chemical implant coated in a layer of polymer releasing the medication (InnoRx/Surmodic), or else are bioerodable/biodegradable (Surodex® from Oculex, now Allergan). One of the drawbacks of this type of device is that they move freely in the vitreous humor and run the risk of touching the retina, thereby locally increasing the concentration of medication, possibly up to a toxic level. Although it is possible to suture the implant, that requires an incision that is relatively large (5 millimeters (mm)). Another drawback is the need for regular replacement. Finally, it is not possible to interrupt or to accelerate the treatment as a function of how the pathology responds to treatment.        
Ocular iontophoresis is another technique for local administration of medication into the eye, and it enables most of the drawbacks of the other techniques mentioned above to the mitigated. It also makes it possible in non-invasive manner to obtain concentrations and residence times in the eye that are equal to or greater than prior techniques.
Iontophoresis devices are typically constituted by a direct current (DC) electric field source coupled to two electrodes referred to respectively as “active” and “passive” electrodes. The active electrode acts on an electrolyte containing the active principle(s), while the passive electrode serves as a return electrode and enables the electric circuit to be looped through the patient's body.